Zoom lens

Details Zoom lens Zoom lens

1995-03-07

1997-03-18

Epps, Georgia Y.

Optical: systems and elements

Lens

With variable magnification

G02B 1514

Patent

active

056128258

ABSTRACT:
A zoom lens of the rear focus type is disclosed comprising, from front to rear, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power, the second and fourth lens units axially moving to effect zooming, and the fourth lens unit axially moving to effect focusing. The third lens unit includes at least one positive lens at a front position and a negative lens of meniscus form concave toward the image side at a rearmost position. The fourth lens unit includes one negative lens and two positive lenses. The focal lengths f3 and f4 of the third and fourth lens units, respectively, satisfy the following condition:

REFERENCES:
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patent: 4854684 (1989-08-01), Horiuchi
patent: 4859042 (1989-08-01), Tanaka
patent: 4892397 (1990-01-01), Horiuchi
patent: 5011272 (1991-04-01), Nakayama et al.
patent: 5095387 (1992-03-01), Horiuchi
patent: 5138492 (1992-08-01), Hamano et al.
patent: 5321552 (1994-06-01), Horiuchi et ak.
patent: 5353157 (1994-10-01), Horiuchi
patent: 5430576 (1995-07-01), Hamano

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